Method and Apparatus for Regenerating Engine Exhaust Filters

ABSTRACT

Internal combustion engine exhaust filter devices and the like are regenerated by placement in a reclamation or burn-off furnace, raising the temperature to at least about 800° F. to 900° F. and conducting relatively low volumes of low pressure air through the filter media to combust entrapped particulates and other materials residing on the filter media. The reclamation furnace includes an afterburner for combusting materials discharged from the filter devices into the furnace chamber so that complete combustion of materials is accomplished before discharge from the furnace. The flow of combustion air for the filter devices is controlled by manifolding and valving connected to a source and the oxygen content of combustion air may be enhanced by a separate source of oxygen injected into the combustion air flow stream.

BACKGROUND OF THE INVENTION

Regulatory authorities around the world have established that emissionsfrom internal combustion engines, including gasoline and diesel engines,will be regulated. Diesel and gasoline engine exhaust streams presentunique filtration problems. The only solution to these problems is thedevelopment of a particulate (soot) filter to extract particulatematerial from the exhaust stream. However, filters which include fluidand particulate filtration media, typically ceramic honeycomb typestructures, eventually become clogged with matter trapped by the mediaand such filters must either be discarded or subjected to a timeconsuming and expensive regeneration or cleaning process. The capitalcost of such filters is not inconsequential, as compared withconventional engine intake air filters and the like, for example.Accordingly, discarding engine exhaust filters is expensive andregeneration of the filter media is desirable. The present inventionprovides an improved method and apparatus for regenerating or cleaningfilters, including ceramic filters for gasoline and diesel engines, inparticular.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for cleaning or regeneratingfluid filters, particularly internal combustion engine exhaust filtersconstructed of metal or ceramic housings and typically including ceramicporous filter media disposed therein.

The present invention also provides an improved method for regeneratingor cleaning filters, particularly exhaust filters which are subject toaccumulations of soot and other particulates generated during thecombustion of hydrocarbon fuels in reciprocating piston and turbineengines.

In accordance with one aspect of the present invention, a furnace isprovided for producing substantial heat to be transmitted to engineexhaust filter devices and the like which are placed within the furnace,the filter devices being subjected to a substantial temperature riseover the exterior thereof and substantial heating of the filter media.Material trapped by the filter media is removed by incineration from theheat generated by the furnace and from pumping a quantity of combustionair to the interior of the filter device to incinerate accumulated soot,and other particulate matter which has been trapped by the filter media.Combustion products from incinerating material accumulated on the filtermedia are conducted through a suitable treatment process as part of thefurnace operation, which process includes flow of filter combustionproducts and other material through an afterburner for furtherincineration of material removed from the filter media.

In accordance with another aspect of the present invention, a somewhatconventional reclamation or “burn-off” type furnace is provided which ismodified to support one or more engine exhaust filter devicestherewithin and to be connected to a source of low pressure air fromexterior of the furnace to provide for combusting or incinerating,within the furnace, material accumulated on the media of the filterdevices.

In accordance with still another aspect of the present invention, areclamation or burn-off type furnace is provided which includes pluralconduits for supplying combustion air in relatively low volumes and atlow pressures directly to plural engine exhaust filters disposed in thefurnace. The source of combustion air is external to the burn-offfurnace and such air is conducted to the filter devices to be treated bysuitable conduits which extend through the furnace wall, preferably,from a manifold connected to the source. During operation, as thereclamation or burn-off furnace heats the filter devices to a suitabletemperature, air flowing directly through the filter devices suppliesoxygen so that carbon soot and any other trapped material within thefilter's ceramic honeycomb structure will be incinerated and removed ascombustion products in gaseous form. The speed and completeness ofreclamation, regeneration or cleaning of the filter media may beenhanced by increasing the concentration of oxygen in the combustion airsupplied to the interiors of the filter devices.

Those skilled in the art will further appreciate the above-mentionedadvantages and superior features of the invention together with otherimportant aspects upon reading the detailed description which follows inconjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING

The drawing figure is a somewhat schematic diagram of an apparatus forregenerating engine exhaust filters and the like in accordance with theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the description which follows, like parts are marked throughout thespecification and drawing with the same reference numerals,respectively. The drawing figure is not intended to be to scale andcertain features may be shown in somewhat schematic or generalized formin the interest of clarity and conciseness.

Referring to the drawing figure, there is illustrated in somewhatschematic form, a so-called reclamation or burn-off furnace 10comprising an insulated, rectangular box-like structure 12 having a topwall 14, a bottom wall 16, opposed sidewalls 18 and 20 and oppositeopposed sidewalls, not shown. One of the sidewalls not shown may includea suitable door for access to the furnace interior. The drawing figuremay be considered to be a vertical central section view through atypical rectangular or square box-like structure comprising the housing12. Furnace 10 includes a primary heating element or burner 22 forgenerating a flame 23 and connected to a source of fuel, not shown, byway of a suitable controller 24. Typical sources of fuel for burner 22would be liquid hydrocarbon or gaseous hydrocarbon fuels, for example.Combustion takes place in a burner housing 26 and combustion products,primarily heated air, carbon dioxide and water vapor are emitted into achamber 28 via one or more ports 27. Airflow into burner housing 26 andair flow out of the burner housing into the chamber 28 takes place in aconventional manner. In fact, the reclamation or burn-off furnaceillustrated may be similar in some respects to that described in U.S.Pat. No. 4,270,898 to Kelly, issued Jun. 2, 1981 to the assignee of thepresent invention.

Burn-off furnace 10 includes a secondary burner 30 also operablyconnected to the controller 24 for generating a flame 31 in a secondaryor afterburner housing 32. Heated air and combustion products generatedin and existing in the chamber 28 flow through an opening or port 33,and are preferably subjected to secondary combustion prior to beingvented through a stack 34 so that emissions from stack 34 comprise,essentially, inert gasses and water vapor. Temperature sensor 38monitors the temperature in the chamber 28 so that controller 24 mayadjust the intensity of heating being carried out by the burners 22 and30. Temperature conditions in chamber 28 and stack 34 may also becontrolled by a water spray controller 40 operably connected to thetemperature sensor 36 and operable to provide a fine spray of water 42by way of a nozzle 44 extending within the chamber 28.

Referring further to the drawing figure, a suitable rack or similarsupport structure 50 is disposed within the chamber 28 for supportingone or more engine exhaust filters, each designated by the numeral 52.The exhaust filters 52 are each characterized by a substantiallycylindrical metal outer housing 53, an inlet port 54, an exhaust port 55and a ceramic honeycomb filter media 56 disposed within the housing 53for trapping particulate material emitted by internal combustionengines, such as gasoline and diesel engines of both piston and turbinetypes, for example. The exhaust filters 52 may be one of several typescommercially available. The filters 52 are disposed for exposure toheated gasses circulating within the chamber 28 between burner outletport 27 and burner inlet port 33. The filters 52 may be mountedhorizontally, as shown, vertically or inclined. Vertical orientationwith the exhaust ports facing upward may be preferred.

It has been determined in accordance with the invention thatparticulates and other materials formed by or including unburned orpartially combusted hydrocarbon fuels, and trapped by the filter media56 of the filters 52, may be removed from the media by raising thetemperature of the media to about 800° F. to 900° F., or possibly highertemperatures, for predetermined periods of time. However, it has alsobeen determined that thorough regeneration or cleaning of the filtermedia 56 is enhanced and the time for cleaning is shortened bycirculating relatively low volumes of low pressure gas, such as ambientair, through the filter devices 52. In accordance with the invention,the apparatus 10 is preferably provided with a relatively low pressureblower or air pump 60 operable to intake ambient air and dischargepressure air to a manifold 62. Respective conduits 64, operablyconnected to manifold 62, extend through furnace wall 12 and aresuitably sealed to prevent escape of combustion gasses from chamber 28.Conduits 64 may be connected to suitable sections of flexible conduits66 which are releasably connected directly to the inlet ports 54 of thefilter units 52 by way of suitable fittings 67, as generally shown inthe drawing figure. Other arrangements of manifolding and connecting thefilter units 52 to a source of low pressure air may be provided withoutdeparting from the invention. For example, the conduits 64 and 66 may beof sufficient length, or connected to respective heat exchanger means,not shown, so as to preheat the air flowing through the filters 52,preferably using heat generated in chamber 28.

In instances when the oxygen content of ambient air supplied by manifold62 is not sufficient to burn off or incinerate all of the material orresidue trapped by the filter elements or media 56, the air conductedthrough the filter elements by way of the manifold 62 and the respectiveconduits 64, 66 may be enriched by a source of oxygen 70 connected tothe manifold 62 by way of a suitable control valve 72. In like mannereach of the conduits 64 is also provided with a suitable control valve74 so that the volume of air being conducted to each one of the filterdevices 52 may be appropriately adjusted. A suitable check valve 76 maybe interposed the manifold 62 and the blower or air pump 60.

Accordingly, in operation, the filter devices 52 may be placed in thechamber 28 and connected to the manifold 62 by way of the respectiveconduits 64, 66 and fittings 67. A source of combustion air containingambient concentrations of oxygen or enhanced concentrations of oxygenmay be conducted through the filter devices 52 while the temperature inthe chamber 28 is raised to a suitable value, such as at least about800° F. to 900° F. in order to oxidize or combust carbonaceous materialin the filters 52. The overall method of cleaning the filter devices 52in accordance with the invention is believed to be more efficient inthat the temperature in the chamber 28 is not required to be raised ashigh and for as long a period of time as with prior art reclamationprocesses, since a suitable flow of combustion air is being supplied tothe interior of the filter devices 52 in a forced manner. Of course, ascombustion air flowing through the filter devices 52 exits therespective filter devices into the chamber 28 and flows to theafterburner 32, any material removed from the filter devices 52 willnormally be further oxidized, if possible, since operating temperatureswithin the secondary or afterburner 32 may, typically, be in the rangeof 1200° F. to 1400° F. Typical volumes for combustion air to beconducted through the filter devices 52 range from about fifty cubicfeet per hour to one hundred fifty cubic feet per hour for filters ofsizes used in applications for over-the-road motor truck dieselpropulsion engines, for example. Of course, the size of the filterdevices 52 and the treatment time desired will dictate, to some extent,the volume of combustion air supplied by the blower or pump 60 and thepressurized oxygen source 70, if used, for example.

The construction and operation of the reclamation or burn-off furnace 10and the method of the present invention are believed to be readilyunderstandable to one of ordinary skill in the art based on theforegoing description. Although preferred embodiments of the inventionhave been described in detail sufficient to enable one skilled in theart to practice the invention, it will be appreciated that varioussubstitutions and modifications may be made without departing from thescope and spirit of the appended claims.

1-17. (canceled)
 18. A method for a regenerating engine exhaust filterdevice having a housing, a porous filter media disposed within saidhousing contaminated with soot and materials entrained in combustionproducts of an engine, said apparatus comprising: a burn-off furnaceincluding an enclosure defining a heating chamber, wherein said furnaceincludes a support in said chamber for supporting plural filter devices,and said apparatus includes a manifold for supplying pressure air tosaid filter devices via conduits operable to be connected to saidmanifold and said filter devices, respectively; a conduit extending fromthe exterior of said air closure to said chamber for connection to saidfilter device; and a source of oxygen containing gas connected to saidconduit for conduction to the interior of said filter device duringheating thereof to incinerate material accumulated on said filter media,comprising: placing a filter device in a burn-off furnace comprising anenclosure defining a chamber in which heated gasses are circulated;heating said filter device by circulating heated gasses within saidchamber; and circulating combustion air through the interior of saidfilter device to incinerate material trapped by filter media of saidfilter device.
 19. The method set forth in claim 18 including the stepof: connecting said filter device to a source of relatively low pressurecombustion air exterior of said chamber and circulating said combustionair through said filter media while heating said filter media withheated gasses within said chamber.
 20. The method set forth in claim 19including the step of: raising the temperature of said filter device toat least about 800° F.
 21. The method set forth in claim 19 includingthe step of: providing said combustion air as ambient air by way of ablower.
 22. The method set forth in claim 21 including the step of:providing a fitting within said chamber for connecting said source ofcombustion air to an inlet port of said filter device.
 23. The methodset forth in claim 18 including the step of: enhancing the oxygencontent of said combustion air prior to introducing said combustion airto the interior of said filter device.
 24. The method set forth in claim18 including the step of: discharging said combustion air and combustionproducts from said filter device into said chamber, mixing saidcombustion products and said heated gasses and conducting saidcombustion products and heated gasses through a burner prior todischarging said combustion products and said heated gasses from saidfurnace.
 25. The method set forth in claim 18 including the step of:preheating said combustion air prior to introduction of said combustionair into said filter device.
 26. The method set forth in claim 25wherein: said combustion air is preheated by heat exchange with saidheated gasses in said chamber.